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Du lancement de jets MHD aux rayons cosmiques: La fonction de la turbulence magnetique

Abstract : The first part of my thesis shows how Keplerian discs can launch MHD jets, under some conditions. The key points of this first part are the adding of viscosity inside the disc and a relevant energy equation, In particular, I have shown both analytically and numerically that the angular momentum transport is constrained by the MHD turbulence properties. I have also shown that one must take into account a relevant energy equation in order to have a more realistic description of jets observed in the Universe. Moreover, some energy turbulent transport mechanisms cannot be described in a simple MHD approach. In order to better understand the interaction between a turbulent magnetic field and charged particles, I have undertaken a study dealing with spatial and angular diffusion of hadrons with a chaotic magnetic field generated by a magnetic turbulence. In this study, it clearly appears that the spatial diffusion coefficient along the mean magnetic field extrapolate the results of quasi-linear theory for weak turbulence. At the opposite, in the inertial range, the spatial diffusion coefficient across the mean magnetic field is inconsistent with such a theory. Indeed the spatial diffusion coefficient across the mean magnetic field has a behaviour that can be interpreted as a chaotic diffusion regime as the one predicted by Rechester & Rosenbluth. Moreover, outside this range, the behaviours of all spatial diffusion coefficients are different of those expected in the framework of quasi-linear theory. At last, it has been found that a Bohm diffusion regime never occurs whatever the magnetic chaos.
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https://tel.archives-ouvertes.fr/tel-00006183
Contributor : Fabien Casse <>
Submitted on : Wednesday, June 2, 2004 - 2:52:37 PM
Last modification on : Friday, November 6, 2020 - 4:04:56 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:35:24 PM

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  • HAL Id : tel-00006183, version 1

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Fabien Casse. Du lancement de jets MHD aux rayons cosmiques: La fonction de la turbulence magnetique. Astrophysique [astro-ph]. Université Joseph-Fourier - Grenoble I, 2001. Français. ⟨tel-00006183⟩

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